Spheres Multiple Physical Network-Based Triboelectric Materials for Self-Powered Contactless Sensing

Triboelectric tactile sensor for pressure and temperature sensing in high-temperature applications

Skin-like sensors capable of detecting multiple stimuli simultaneously have great potential in cutting-edge human-machine interaction. However, realizing multimodal tactile recognition beyond human tactile perception still faces significant challenges. Here, an extreme environments-adaptive multimodal triboelectric sensor was developed, capable of detecting pressure/temperatures beyond the range of human perception. Based on triboelectric nanogenerator technology, an asymmetric structure capable of independently outputting dual signals was designed to improve perception sensitivity. By converting the signals and the stimuli into feature matrices, parallel perception of complex objects (with a recognition rate of 94%) and temperature at high temperatures was achieved. The proposed multimodal triboelectric tactile sensor represents progress in maximum detection range and rapid response, realizing the upper limit of human skin's high-temperature sensing (60 °C) with a working temperature of 200 °C. The proposed self-powered multimodal sensing system offers a wider range of possibilities for human/robot/environment interaction applications.

A Review on MXene/Nanocellulose Composites: Toward Wearable Multifunctional Electromagnetic Interference Shielding Application

With the rapid development of mobile communication technology and wearable electronic devices, the electromagnetic radiation generated by high-frequency information exchange inevitably threatens human health, so high-performance wearable electromagnetic interference (EMI) shielding materials are urgently needed. The 2D nanomaterial MXene exhibits superior EMI shielding performance owing to its high conductivity, however, its mechanical properties are limited due to the high porosity between MXene nanosheets. In recent years, it has been reported that by introducing natural nanocellulose as an organic framework, the EMI shielding and mechanical properties of MXene/nanocellulose composites can be synergically improved, which are expected to be widely used in wearable multifunctional shielding devices. In this review, the electromagnetic wave (EMW) attenuation mechanism of EMI shielding materials is briefly introduced, and the latest progress of MXene/nanocellulose composites in wearable multifunctional EMI shielding applications is comprehensively reviewed, wherein the advantages and disadvantages of different preparation methods and various types of composites are summarized. Finally, the challenges and perspectives are discussed, regarding the performance improvement, the performance control mechanism, and the large-scale production of MXene/nanocellulose composites. This review can provide guidance on the design of flexible MXene/nanocellulose composites for multifunctional electromagnetic protection applications in the future intelligent wearable field.

Biowaste-Derived Triboelectric Nanogenerators for Emerging Bioelectronics

Triboelectric nanogenerators (TENGs) combine contact electrification and electrostatic induction effects to convert waste mechanical energy into electrical energy. As conventional devices contribute to electronic waste, TENGs based on ecofriendly and biocompatible materials have been developed for various energy applications. Owing to the abundance, accessibility, low cost, and biodegradability of biowaste (BW), recycling these materials has gained considerable attention as a green approach for fabricating TENGs. This review provides a detailed overview of BW materials, processing techniques for BW-based TENGs (BW-TENGs), and potential applications of BW-TENGs in emerging bioelectronics. In particular, recent progress in material design, fabrication methods, and biomechanical and environmental energy-harvesting performance is discussed. This review is aimed at promoting the continued development of BW-TENGs and their adoption for sustainable energy-harvesting applications in the field of bioelectronics.

Multi-receptor skin with highly sensitive tele-perception somatosensory

The limitations and complexity of traditional noncontact sensors in terms of sensitivity and threshold settings pose great challenges to extend the traditional five human senses. Here, we propose tele-perception to enhance human perception and cognition beyond these conventional noncontact sensors. Our bionic multi-receptor skin employs structured doping of inorganic nanoparticles to enhance the local electric field, coupled with advanced deep learning algorithms, achieving a ΔV/Δd sensitivity of 14.2, surpassing benchmarks. This enables precise remote control of surveillance systems and robotic manipulators. Our long short-term memory-based adaptive pulse identification achieves 99.56% accuracy in material identification with accelerated processing speeds. In addition, we demonstrate the feasibility of using a two-dimensional (2D) sensor matrix to integrate real object scan data into a convolutional neural network to accurately discriminate the shape and material of 3D objects. This promises transformative advances in human-computer interaction and neuromorphic computing.

Phase-Directed Assembly of Triboelectric Nanopaper for Self-Powered Noncontact Sensing

Noncontact sensing technology serves as a pivotal medium for seamless data acquisition and intelligent perception in the era of the Internet of Things (IoT), bringing innovative interactive experiences to wearable human-machine interaction perception networks. However, the pervasive limitations of current noncontact sensing devices posed by harsh environmental conditions hinder the precision and stability of signals. In this study, the triboelectric nanopaper prepared by a phase-directed assembly strategy is presented, which possesses low charge transfer mobility (1618 cm2 V-1 s-1) and exceptional high-temperature stability. Wearable self-powered noncontact sensors constructed from triboelectric nanopaper operate stably under high temperatures (200 °C). Furthermore, a temperature warning system for workers in hazardous environments is demonstrated, capable of nonintrusively identifying harmful thermal stimuli and detecting motion status. This research not only establishes a technological foundation for accurate and stable noncontact sensing under high temperatures but also promotes the sustainable intelligent development of wearable IoT devices under extreme environments.

Advanced Applications of Porous Materials in Triboelectric Nanogenerator Self-Powered Sensors

Porous materials possess advantages such as rich pore structures, a large surface area, low relative density, high specific strength, and good breathability. They have broad prospects in the development of a high-performance Triboelectric Nanogenerator (TENG) and self-powered sensing fields. This paper elaborates on the structural forms and construction methods of porous materials in existing TENG, including aerogels, foam sponges, electrospinning, 3D printing, and fabric structures. The research progress of porous materials in improving TENG performance is systematically summarized, with a focus on discussing design strategies of porous structures to enhance the TENG mechanical performance, frictional electrical performance, and environmental tolerance. The current applications of porous-material-based TENG in self-powered sensing such as pressure sensing, health monitoring, and human-machine interactions are introduced, and future development directions and challenges are discussed.

Emerging Trends of Nanofibrous Piezoelectric and Triboelectric Applications: Mechanisms, Electroactive Materials, and Designed Architectures

Over the past few decades, significant progress in piezo-/triboelectric nanogenerators (PTEGs) has led to the development of cutting-edge wearable technologies. Nanofibers with good designability, controllable morphologies, large specific areas, and unique physicochemical properties provide a promising platform for PTEGs for various advanced applications. However, the further development of nanofiber-based PTEGs is limited by technical difficulties, ranging from materials design to device integration. Herein, the current developments in PTEGs based on electrospun nanofibers are systematically reviewed. This review begins with the mechanisms of PTEGs and the advantages of nanofibers and nanodevices, including high breathability, waterproofness, scalability, and thermal-moisture comfort. In terms of materials and structural design, novel electroactive nanofibers and structure assemblies based on 1D micro/nanostructures, 2D bionic structures, and 3D multilayered structures are discussed. Subsequently, nanofibrous PTEGs in applications such as energy harvesters, personalized medicine, personal protective equipment, and human-machine interactions are summarized. Nanofiber-based PTEGs still face many challenges such as energy efficiency, material durability, device stability, and device integration. Finally, the research gap between research and practical applications of PTEGs is discussed, and emerging trends are proposed, providing some ideas for the development of intelligent wearables.

Proximity Sensing Electronic Skin: Principles, Characteristics, and Applications

The research on proximity sensing electronic skin has garnered significant attention. This electronic skin technology enables detection without physical contact and holds vast application prospects in areas such as human-robot collaboration, human-machine interfaces, and remote monitoring. Especially in the context of the spread of infectious diseases like COVID-19, there is a pressing need for non-contact detection to ensure safe and hygienic operations. This article comprehensively reviews the significant advancements in the field of proximity sensing electronic skin technology in recent years. It covers the principles, as well as single-type proximity sensors with characteristics such as a large area, multifunctionality, strain, and self-healing capabilities. Additionally, it delves into the research progress of dual-type proximity sensors. Furthermore, the article places a special emphasis on the widespread applications of flexible proximity sensors in human-robot collaboration, human-machine interfaces, and remote monitoring, highlighting their importance and potential value across various domains. Finally, the paper provides insights into future advancements in flexible proximity sensor technology.

Dielectric-Enhanced, High-Sensitivity, Wide-Bandwidth, and Moisture-Resistant Noncontact Triboelectric Sensor for Vibration Signal Acquisition

Noncontact triboelectric sensors (TESs) have the potential to enhance self-powered sensing performance by eliminating the need for physical contact. This study demonstrates a strategy to construct noncontact TES that enables self-powered sensing and vibration signal acquisition with high sensitivity and wide bandwidth. The incorporation of carbon nanotubes into nitrocellulose (CNTs/NC) endows the tribopositive layer with larger inner micro/nanocapacitances, consequently augmenting the charge storage capacity. As a result, the contactless sensing performance of CNTs/NC-based TES (CNTs/NC-TES) was enhanced by 146%. Correspondingly, the related theory and working mechanism of noncontact sensing were demonstrated. Furthermore, the CNTs/NC-TES exhibits optimal distance response sensitivity of 57.10 V mm-1, a wide-bandwidth response from 0.1 to 4000 Hz, and relative humidity (RH) stability. This contactless CNTs/NC-TES has the potential for high sensitivity and wide frequency vibration monitoring in a high-RH environment.

Highly porous and rough polydimethylsiloxane film-based triboelectric nanogenerators and its application for electrochemical cathodic protection

The development and utilization of triboelectric nanogenerator (TENG) are very important for realizing energy cleaning in electrochemical processes. However, limited electrical output performance plays a major stumbling block to this process. Herein, a porous and high-roughness PDMS (PR/PDMS) negative friction layer was obtained by doping PDMS with powdered chitosan and casting using a sacrificial anodic alumina template. A TENG was fabricated by the PR/PDMS with Al film (PR-TENG). The PR-TENG exhibited much better performance than the pure PDMS-based TENG, which was attributed to the porous properties of the PR/PDMS. Under the driving of external mechanical force at 5 Hz, the PR-TENG showed a maximum output open-circuit voltage (Voc) and short-circuit current density (Jsc) of 77.1 V and 33.9 mA/m2, respectively. To prove the concept, the electrochemical cathodic protection system with PR-TENG was constructed. Ultimately, the application prospects of the PR-TENG as a clean energy source for electrochemical processes were explored and evaluated.

Self-Powered TENG with High Humidity Sensitivity from PVA Film Modified by LiCl and MXene

Triboelectric nanogenerators (TENGs) are promising for a variety of applications that require a reliable output performance and stability. In this work, by utilizing the synergistic effect of lithium chloride (LiCl) and MXene, poly(vinyl alcohol) (PVA) based composite films with humidity-sensitive properties were prepared and employed as a friction layer to achieve self-powered TENGs with enhanced output performance under high humidity. The composite material demonstrates exceptional and stable output performance in the humidity range of 30-95% while exhibiting a strong linear correlation with increasing relative humidity (RH). At 95% RH, its short-circuit current increases up to 31.91 μA, which is three times the output of the TENG fabricated by PVA and PTFE (P-TENG). The rich hydroxyl group in PVA, the strong hygroscopicity of LiCl, and the microcapacitor network provided by MXene nanosheets significantly improve the water absorption capacity and surface roughness of the composite material, resulting in an excellent triboelectric output of TENG. Short-circuit current of the TENG in a wide range of RH (from 50% to 98%) responds very sensitively to humidity fluctuations in the environment and superior adsorption-desorption performance as humidity decreases. Furthermore, TENG regarded as a power supply in high humidity conditions was realized and it can light up 240 LEDs instantaneously with the transfer charge density of TENG reaching 194.37 μC m-2. This technology presents an effective method for stable energy harvesting and self-powered sensing in fog, the ocean, and other high-humidity environments.

Recent Advances in Triboelectric Nanogenerators: From Technological Progress to Commercial Applications

Serious climate changes and energy-related environmental problems are currently critical issues in the world. In order to reduce carbon emissions and save our environment, renewable energy harvesting technologies will serve as a key solution in the near future. Among them, triboelectric nanogenerators (TENGs), which is one of the most promising mechanical energy harvesters by means of contact electrification phenomenon, are explosively developing due to abundant wasting mechanical energy sources and a number of superior advantages in a wide availability and selection of materials, relatively simple device configurations, and low-cost processing. Significant experimental and theoretical efforts have been achieved toward understanding fundamental behaviors and a wide range of demonstrations since its report in 2012. As a result, considerable technological advancement has been exhibited and it advances the timeline of achievement in the proposed roadmap. Now, the technology has reached the stage of prototype development with verification of performance beyond the lab scale environment toward its commercialization. In this review, distinguished authors in the world worked together to summarize the state of the art in theory, materials, devices, systems, circuits, and applications in TENG fields. The great research achievements of researchers in this field around the world over the past decade are expected to play a major role in coming to fruition of unexpectedly accelerated technological advances over the next decade.

Rational Design of Cellulosic Triboelectric Materials for Self-Powered Wearable Electronics

With the rapid development of the Internet of Things and flexible electronic technologies, there is a growing demand for wireless, sustainable, multifunctional, and independently operating self-powered wearable devices. Nevertheless, structural flexibility, long operating time, and wearing comfort have become key requirements for the widespread adoption of wearable electronics. Triboelectric nanogenerators as a distributed energy harvesting technology have great potential for application development in wearable sensing. Compared with rigid electronics, cellulosic self-powered wearable electronics have significant advantages in terms of flexibility, breathability, and functionality. In this paper, the research progress of advanced cellulosic triboelectric materials for self-powered wearable electronics is reviewed. The interfacial characteristics of cellulose are introduced from the top-down, bottom-up, and interfacial characteristics of the composite material preparation process. Meanwhile, the modulation strategies of triboelectric properties of cellulosic triboelectric materials are presented. Furthermore, the design strategies of triboelectric materials such as surface functionalization, interfacial structure design, and vacuum-assisted self-assembly are systematically discussed. In particular, cellulosic self-powered wearable electronics in the fields of human energy harvesting, tactile sensing, health monitoring, human-machine interaction, and intelligent fire warning are outlined in detail. Finally, the current challenges and future development directions of cellulosic triboelectric materials for self-powered wearable electronics are discussed.

Fabrication of Advanced Cellulosic Triboelectric Materials via Dielectric Modulation

The rapid rise of triboelectric nanogenerators (TENGs), which are emerging energy conversion devices in advanced electronics and wearable sensing systems, has elevated the interest in high-performance and multifunctional triboelectric materials. Among them, cellulosic materials, affording high efficiency, biodegradability, and customizability, are becoming a new front-runner. The inherently low dielectric constant limits the increase in the surface charge density. However, owing to its unique structure and excellent processability, cellulose shows great potential for dielectric modulation, providing a strong impetus for its advanced applications in the era of Internet of Things and artificial intelligence. This review aims to provide comprehensive insights into the fabrication of dielectric-enhanced cellulosic triboelectric materials via dielectric modulation. The exceptional advantages and research progress in cellulosic materials are highlighted. The effects of the dielectric constant, polarization, and percolation threshold on the charge density are systematically investigated, providing a theoretical basis for cellulose dielectric modulation. Typical dielectric characterization methods are introduced, and their technical characteristics are analyzed. Furthermore, the performance enhancements of cellulosic triboelectric materials endowed by dielectric modulation, including more efficient energy harvesting, high-performance wearable electronics, and impedance matching via material strategies, are introduced. Finally, the challenges and future opportunities for cellulose dielectric modulation are summarized.

Wearable Triboelectric Visual Sensors for Tactile Perception

Tactile sensors with visible light feedback functions, such as wearable displays and electronic skin and biomedical devices, are becoming increasingly important in various fields. However, existing methods cannot meet the application requirements for the tactile perception of intensity feedback and extended intersection due to their limited light-mapping performance and insufficient portability. Herein, a freely constructible self-powered visual tactile sensor is proposed, which consists of a high-output triboelectric nanogenerator (TENG) and a visual light source. The transferred charge of the TENG is enhanced to 746 nC by the structural design of the triboelectric material and device, which can easily drive the light source to generate a light signal with a brightness of 9.8 cd m^-2 . Notably, the application of the TENG enables to realization visual sensing of the palm-grasp state and strength feedback without an external power supply. This visual feedback and power-free tactile sensors are expected to have potential application in the field of artificial intelligence as a new interactive medium for smart protective clothing and robotics.

Rational Design of Advanced Triboelectric Materials for Energy Harvesting and Emerging Applications

The properties of materials play a significant role in triboelectric nanogenerators (TENGs). Advanced triboelectric materials for TENGs have attracted tremendous attention because of their superior advantages (e.g., high specific surface area, high porosity, and customizable macrostructure). These advanced materials can be extensively applied in numerous fields, including energy harvester, wearable electronics, filtration, and self-powered sensors. Hence, designing triboelectric materials as advanced functional materials is important for the development of TENGs. Herein, the structural modification methods based on electrospinning to improve the triboelectric properties and the latest research progress in this kind of TENGs are systematically summarized. Preparation methods and design trends of nanofibers, microspheres, hierarchical structures, and doping nanomaterials are highlighted. The factors influencing the formation and properties of triboelectric materials are considered. Furthermore, the latest progress on the applications of TENGs is systematically elaborated. Finally, the challenges in the development of triboelectric materials are discussed, thereby guiding researchers in the large-scale application of TENGs.

Gas-Sensitive Cellulosic Triboelectric Materials for Self-Powered Ammonia Sensing

Gas-sensitive materials are capable of dynamic identification and content monitoring of specific gases in the environment, and their applications in the field of gas sensing are promising. However, weak adsorption properties are the main challenge limiting the application of gas-sensitive materials. A highly adsorbent gas-sensitive cellulose nanofibril (CNF)-based triboelectric material with a layered structure is prepared here and it is applied to self-powered gas sensing. The layered structure of the triethoxy-1H,1H,2H,2H-tridecafluoro-n-octylsilane cellulose nanofiber (PFOTES-CNF)-based gas-sensitive material further enhances the adsorption of the material due to electrostatic adsorption in the electrostatic field induced by triboelectricity. It is found that the ammonia-sensitive material obtained by loading Ti3 C2 Tx in PFOTES-CNF has a fast response/recovery (12/14 s), high sensitivity response (Vair /Vgas  = 2.1), high selectivity response (37.6%), and low detection limit (10 ppm) for 100 ppm of ammonia gas. In addition, the ammonia-sensitive CNF-based triboelectric material can accurately identify NH3 concentration changes in the range of 10-120 ppm and transmit the signal wirelessly to the user interface, facilitating real-time online monitoring of NH3 in the environment. A novel strategy is provided here for designing and preparing high-performance gas-sensitive composites and the analysis of self-powered gas sensing is guided.

A Self-Powered Triboelectric Nanogenerator Based on Intelligent Interactive System for Police Shooting Training Monitoring and Virtual Reality Interaction

A self-powered triboelectric nanogenerator (SPTENG) based on triboelectric effect and an intelligent interactive system are fabricated for monitoring shooting training and virtual training. The SPTENG is composed of latex and PTFE and an intelligent system. Based on triboelectric effect, the SPTENG can be used to monitor the progress of trigger pressing without a power supply (this is supplied by trigger movements). Because of the flexible properties, it can be attached to a trigger conveniently to monitor the progress of trigger pressing, such as trigger time, trigger stability, etc. Meanwhile, as part of an intelligent shooting system, police can formulate a standard scheme according to signals to improve their skills. Furthermore, they can use it to train between reality and virtuality. Therefore, it has a wide development space in human-computer interaction and real-time information processing.

Hierarchical Porous Cellulosic Triboelectric Materials for Extreme Environmental Conditions

Synthetic polymer materials such as paraformaldehyde and polyamides are widely used in the field of energy engineering. However, they pose a challenge to environmental sustainability because they are derived from petrochemicals that are non-renewable and difficult to degrade in the natural environment. The development of high-performance natural alternatives is clearly emerging as a promising mitigation option. Inspired by natural bamboo, this research reports a "three-step" strategy for the large-scale production of triboelectric materials with special nanostructures from natural bamboo. Benefiting from the special hierarchical porous structure of the material, Bamboo/polyaniline triboelectric materials can reach short-circuit current of 2.9 µA and output power of 1.1 W m^-2 at a working area of only 1 cm² , which exceeds most wood fiber-based triboelectric materials. More importantly, it maintains 85% energy harvesting after an extreme environment of high temperature (200 °C), low temperature (-196 °C), combustion environment, and multiple thermal shocks (ΔT = 396 °C). This is unmatched by current synthetic polymer materials. This work provides new research ideas for the construction and application of biomass structural materials under extreme environmental conditions.